Electrosurgical apparatus with stable coagulation

ABSTRACT

An electrosurgical apparatus supplies high-frequency power from a high-frequency power supply unit to an instrument placed in association with an organic tissue to dissect or coagulate the organic tissue. An impedance calculating section calculates the impedance value of the organic tissue. A rate-of-impedance-change calculating section calculates the rate of impedance change of the organic tissue based on the impedance value calculated by the impedance calculating section. A control section controls the high-frequency output of the high-frequency power supply unit based on a predetermined condition provided by combining the impedance value calculated by the impedance calculating section with the rate of impedance change calculated by the rate-of-impedance-change calculating section.

BACKGROUND OF THE INVENTION

The present invention relates to an electro-surgical apparatus.

There are electrosurgical apparatuses which coagulate or dissect organictissues using high-frequency power. Such an electrosurgical apparatusgenerates high-frequency power inside its main body and supplies thehigh-frequency power to a monopolar instrument or bipolar instrument,connected to the main body, for treatment of organic tissues.

Jpn. Pat. Appln. KOKAI Publication No. 8-196543 discloses an impedancemonitoring apparatus which monitors the impedance of an organic tissuewhile this tissue is being treated with high-frequency power. Morespecifically, this apparatus measures the minimum impedance and uses afunction of this minimum impedance to determine the impedance of thepoint of time when tissue coagulation is completed.

As the electrosurgical apparatus described in the aforementioned Jpn.Pat. Appln. KOKAI Publication No. 8-196543 detects the end of tissuecoagulation based only on the function of the minimum impedance, thedetection result considerably varies depending on the types of tissuesor the clamping state of forceps, which may result in overburning.Apparently, this apparatus cannot guarantee a stable coagulationperformance.

There is another method which detects the end of tissue coagulationusing the rate of change in impedance, but which has a drawback similarto that of the above method of detecting the end of tissue coagulationusing the impedance.

The prior art including the one disclosed in the mentioned Jpn. Pat.Appln. KOKAI Publication No. 8-196543 employs fixed conditions fordetecting the end of tissue coagulation and thus cannot arbitrarilychange the coagulation level.

Accordingly, it is a primary object of the present invention to providean electrosurgical apparatus capable of surely stopping the output atthe end of coagulation to avoid overburning.

It is a secondary object of this invention to provide an electrosurgicalapparatus which can change the coagulation level according to a user'sselection by changing a condition for detecting the end of coagulation.

BRIEF SUMMARY OF THE INVENTION

To achieve the first object, according to the first aspect of thisinvention, there is provided an electrosurgical apparatus for supplyinghigh-frequency power from a high-frequency power supply unit to aninstrument placed in association with an organic tissue to dissect orcoagulate the organic tissue, which said electrosurgical apparatuscomprises:

an impedance calculating section for calculating an impedance value ofthe organic tissue;

a rate-of-impedance-change calculating section for calculating a rate ofimpedance change of the organic tissue based on the impedance valuecalculated by the impedance calculating section; and

a control section for controlling a high-frequency output of thehigh-frequency power supply unit based on a predetermined conditionprovided by an evaluation of both the impedance value calculated by theimpedance calculating section and the rate of impedance changecalculated by the rate-of-impedance-change calculating section.

To achieve the first object, according to the second aspect of thisinvention, there is provided a control apparatus, connected to anelectrosurgical apparatus having an instrument for performing apredetermined treatment on an organic tissue and a high-frequency powersupply unit for supplying high-frequency power for treating the organictissue to the instrument, for controlling the high-frequency poweroutput from the high-frequency power supply unit, which controlapparatus comprises:

an impedance calculating section for calculating an impedance value ofthe organic tissue;

a rate-of-impedance-change calculating section for calculating a rate ofimpedance change of the organic tissue based on the impedance valuecalculated by the impedance calculating section; and

a control section for controlling a high-frequency output of thehigh-frequency power supply unit based on a predetermined conditionprovided by combining the impedance value calculated by the impedancecalculating section with the rate of impedance change calculated by therate-of-impedance-change calculating section.

To achieve the second object, according to the third aspect of thisinvention, there is provided an electrosurgical apparatus for supplyinghigh-frequency power from a high-frequency power supply unit to aninstrument placed in association with an organic tissue to coagulate ordissect the organic tissue, which apparatus comprises:

a setting section for setting a coagulation level comprising at leastone variable representing an end of coagulation in a variable mannerprior to a coagulation operation;

a detection section for detecting a coagulation state of the organictissue in a coagulation operation; and

a control section for controlling a high-frequency output of thehigh-frequency power supply unit based on the coagulation level set bythe setting section and the coagulation state detected by the detectionsection.

To achieve the second object, according to the fourth aspect of thisinvention, there is provided a control apparatus, connected to anelectrosurgical apparatus having an instrument for performing apredetermined treatment on an organic tissue and a high-frequency powersupply unit for supplying high-frequency power for treating the organictissue to the instrument, for controlling the high-frequency poweroutput from the high-frequency power supply unit, which controlapparatus comprises:

a setting section for setting a coagulation level of a tissue in avariable manner;

a detection section for detecting a coagulation state of the organictissue in a coagulation operation; and

a control section for controlling a high-frequency output of thehigh-frequency power supply unit based on the coagulation level set bythe setting section and the coagulation state detected by the detectionsection.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to embodiments of this invention;

FIG. 2 is a diagram showing a monopolar instrument;

FIG. 3 is a diagram for explaining the operations of first to thirdembodiments of this invention;

FIG. 4 is a flowchart illustrating the operation of the first embodimentof this invention;

FIG. 5 is a flowchart showing steps between A and B in FIG. 4;

FIG. 6 is a flowchart illustrating the operation of the secondembodiment of this invention;

FIG. 7 is a flowchart illustrating the operation of the third embodimentof this invention;

FIG. 8 is a diagram (part 1) for explaining the operation of a fourthembodiment of this invention;

FIG. 9 is a diagram (part 2) for explaining the operation of the fourthembodiment of this invention;

FIG. 10 is a flowchart illustrating the operation of the fourthembodiment of this invention;

FIG. 11 is a flowchart illustrating the operation of a fifth embodimentof this invention;

FIG. 12 is a flowchart illustrating the operation of a sixth embodimentof this invention;

FIG. 13 is a flowchart illustrating the operation of a seventhembodiment of this invention;

FIG. 14 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to an eighth embodiment of thisinvention;

FIG. 15 is a diagram showing the structure of a setting input section12;

FIG. 16 is a diagram showing the relationship between the characteristicof a high-frequency current (I) and the output of a power supply circuit10;

FIG. 17 is a diagram for explaining the operation of the eighthembodiment of this invention;

FIG. 18 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to a ninth embodiment of thisinvention;

FIG. 19 is a diagram showing the relationship between the characteristicof a high-frequency output (V) and the output of the power supplycircuit 10;

FIG. 20 is a diagram for explaining the operation of the ninthembodiment of this invention;

FIG. 21 is a diagram (part 1) for explaining the operation of a tenthembodiment of this invention;

FIG. 22 is a diagram (part 2) for explaining the operation of the tenthembodiment of this invention;

FIG. 23 is a diagram for explaining the operation of an eleventhembodiment of this invention;

FIG. 24 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to a twelfth embodiment of thisinvention;

FIG. 25 is a diagram showing the structure of a setting input section 12according to the twelfth embodiment of this invention;

FIG. 26 is a diagram showing an output characteristic when an outputvoltage and an output current are limited; and

FIG. 27 is a diagram showing an output characteristic of power supplyunit.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to embodiments of this invention. Acommercially available power supply 9 is connected to a power supplycircuit 10 which generates desired supply power. Connected to this powersupply circuit 10 are a waveform generator 11 which generates a waveformcorresponding to the output mode according to a procedure and a CPU 13for implementing general control of this electrosurgical apparatus.Connected to the waveform generator 11 and the CPU 13 are an amplifier15 for amplifying a minute-level signal from the waveform generator 11and an output controller 16 for controlling the output of the amplifier15 based on a control signal from the CPU 13.

An output transformer 17 has its primary side connected to the amplifier15 and its secondary side connected to terminals 21 a and 21 b via acurrent sensor 18 and a voltage sensor 19. A bipolar instrument 22 a andbipolar electrode 22 b are connected via active lines to the terminals21 a and 21 b.

Although the bipolar instrument is illustrated as an instrument in FIG.1, a monopolar instrument 23 with a monopolar electrode 23 a may be usedinstead as shown in FIG. 2. In this case, a feedback electrode 25 isconnected to the terminal 21 b via a feedback line.

Connected to the current sensor 18 and voltage sensor 19 is an impedancecalculator 20 which computes an impedance based on a current and avoltage respectively detected by those sensors 18 and 19. The CPU 13 isfurther connected to a foot-operated switch 8, a setting input section12 and an informing section 14.

First Embodiment

A first embodiment of this invention will now be discussed withreference to the accompanying drawings. The first embodiment ischaracterized in that the CPU 13 and output controller 16 control theamplifier 15 to stop the output (automatic stop function) when acombination of the impedance of a tissue computed by the impedancecalculator 20 and the rate of impedance change acquired based on thisimpedance meets a predetermined impedance condition.

FIG. 3 shows the relationship between the characteristic of an impedance(Z) and the output of the power supply circuit 10 and shows that theoutput of the amplifier 15 is stopped when the impedance condition ismet.

The operation of the first embodiment will now be explained referring toa flowchart in FIG. 4.

As the foot-operated switch 8 for starting the power output from theelectrosurgical apparatus is switched ON (step S0), initialization isexecuted (step S1). In this initialization, the output power P1=40 Winput by an operator via the setting input section 12 is set to avariable Pout associated with the output power and 10 KΩ is set to avariable Zmin associated with the minimum impedance value. It is assumedthat an initial impedance Z1 has been set to 500 Ω, an initial rate ofimpedance change dZ1 has been set to+300 Ω/sec and a decision variableCn1=0 and a decision variable Cn2=0 have been set.

Then, it is determined if the foot-operated switch 8 has been switchedOFF (step S2). When the foot-operated switch 8 has been switched OFF,“0” is set to the output power Pout (step S5) after which this flow willbe terminated. When the foot-operated switch 8 has not been switchedOFF, an impedance Z and a rate of impedance change dZ are calculated(step S3). Next, it is determined if the calculated impedance Z issmaller than the minimum impedance value Zmin (step S4).

When the decision is “YES,” the calculated impedance Z is substitutedinto the minimum impedance value Zmin (step S6) and the flow thenreturns to step S2.

When the decision in step S4 is “NO,” on the other hand, the flowproceeds to step S7 in FIG. 5 to determine if the calculated rate ofimpedance change dz is equal to or greater than dZl (+300 Ω/sec in thisexample). When the decision is “YES,” “1” is substituted into thedecision variable Cn1 (step S8) and the flow then proceeds to step S9.When the decision in step S7 is “NO,” the flow immediately proceeds tostep S9.

In step S9, it is determined if the impedance Z is equal to or greaterthan the minimum impedance value Zmin multiplied by 3. When the decisionis “YES,” “1” is substituted into the decision variable Cn2 (step S10)and the flow then proceeds to step S11. When the decision in step S9 is“NO,” the flow immediately proceeds to step S11.

In step S11, it is determined if the product of Cn1 and Cn2 is equal to“1.” When the decision is “YES,” “0” is substituted into the outputpower Pout (step S12), and the informing section 14 outputs a sound(buzzer ON) from a speaker or turns on an LED (step S13) to inform theoperator. This flow is then terminated.

When the decision in step S11 is “NO,” it is determined if the impedanceZ is equal to or greater than the sum of the minimum impedance valueZmin and the initial impedance value Zini (step S14). When the decisionis “YES,” the processes starting at the aforementioned step S12 areexecuted. When the decision in step S14 is “NO,” the flow returns tostep S2 in FIG. 4.

The above-described first embodiment is summarized as follows.

(1) The output is started and the impedance value Z is measured.

(2) The minimum impedance value Zmin is acquired.

(3) The output is stopped when the impedance value Z satisfies eitherone of the following conditions (a) and (b).

(a) The rate of impedance change dz has become equal to or greater than+300 Ω/sec at least once and the impedance value Z has become equal toor greater than the minimum impedance value Zmin multiplied by 3.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and 500Ω.

(4) After the output is stopped in (3) above, the operator is informedthrough a buzzer sound or lit LED.

According to the above-described first embodiment, when the impedancerapidly rises which it indicates the end of coagulation, the condition(a) can surely stop the output. Even if the impedance rises too slowlyto satisfy the condition (a), the output can be stopped using thecondition (b). It is therefore possible to reliably stop the output atthe end of coagulation where there is no overburning.

Second Embodiment

A second embodiment of this invention will now be discussed. FIG. 6 is aflowchart illustrating the operation of the second embodiment. The stepsin FIG. 6 are the same as those in FIG. 5 except that step S9 in FIG. 5is replaced with step S9′ where it is determined if the impedance Z isequal to or greater than the sum of the minimum impedance value Zmin and200 Ω. The second embodiment is therefore summarized as follows.

(1) The output is started and the impedance value Z is measured.

(2) The minimum impedance value Zmin is acquired.

(3) The output is stopped when the impedance value Z satisfies eitherone of the following conditions (a) and (b).

(a) The rate of impedance change dZ has become equal to or greaterthan+300 Ω/sec at least once and the impedance value Z has become equalto or greater than the sum of the minimum impedance value zmin and 200Ω.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and 500 Ω.

(4) After the output is stopped in (3) above, the operator is informedthrough a buzzer sound or lit LED.

According to the above-described second embodiment, the same advantagecan be obtained as that of the first embodiment.

Third Embodiment

A third embodiment of this invention will be discussed below. As theimpedance value significantly varies depending on the types of tissuesor the clamping state of forceps, a single decision condition is notenough to ensure a stable coagulation performance for every case. Tocope with it, the third embodiment is characterized in that thecondition for stopping the output is altered by the minimum impedancevalue. While the flowchart in FIG. 4 is commonly used to describe theoperation of the third embodiment, a flowchart shown in FIG. 7 is usedas a flowchart showing steps between A and B in FIG. 4. As the flowchartin FIG. 4 has already been discussed, only the flowchart in FIG. 7 willbe discussed below.

First, it is determined if the calculated rate of impedance change dZ isequal to or greater than dZ1 (+300 Ω/sec in this example) (step S20).When the decision is “YES,” “1” is substituted into the decisionvariable Cn1 (step S21) and the flow then moves to step S22. When thedecision in step S20 is “NO,” the flow immediately proceeds to step S22.

In step S22, it is determined if the minimum impedance value Zmin isequal to or greater than 100 Ω. When the decision is “YES,” it is thendetermined if the impedance Z is equal to or greater than the minimumimpedance value Zmin multiplied by 3 (step S23). When the decision hereis “YES,” “1” is substituted into the decision variable Cn2 (step S24)and the flow then proceeds to step S26.

When the decision in step S22 is “NO,” it is determined if the impedancez is equal to or greater than the sum of the minimum impedance valueZmin and 200 Ω (step S25). When the decision is “YES,” theaforementioned step S24 is carried out before the flow advances to stepS26. When the decision in step S25 is “NO,” the flow immediatelyproceeds to step S26.

In step S26, it is determined if Cn1×Cn2 is equal to “1.” When thedecision is “YES,” “0” is substituted into the output power Pout (stepS27), and the informing section 14 outputs a sound (buzzer ON) from thespeaker or turns on the LED (step S28) to inform the operator. This flowis then terminated.

When the decision in step S26 is “NO,” it is determined if the impedanceZ is equal to or greater than the sum of the minimum impedance valueZmin and the initial impedance value Zini (500 Ω in this example) (stepS29). When the decision is “YES,” the flow goes to the aforementionedstep S27. When the decision in step S29 is “NO,” the flow returns tostep S2 in FIG. 4.

The above-described third embodiment is summarized as follows.

(1) The output is started and the impedance value z is measured.

(2) The minimum impedance value Zmin is acquired.

(3) The output is stopped when the impedance value Z satisfies eitherone of the following conditions (a) and (b).

Case A where the minimum impedance value Zmin is smaller than 100 Ω:

(a) The rate of impedance change dZ has become equal to or greaterthan+300 Ω/sec at least once and the impedance value Z has become equalto or greater than the sum of the minimum impedance value Zmin and 200Ω.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and 500 Ω.

Case B where the minimum impedance value Zmin is equal to or greaterthan 100 Ω:

(a) The rate of impedance change dZ has become equal to or greaterthan+300 Ω/sec at least once and the impedance value Z has become equalto or greater than the minimum impedance value Zmin multiplied by 3.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and 500 Ω.

(4) After the output is stopped in (3) above, the operator is informedthrough a buzzer sound or lit LED.

According to the above-described third embodiment, when the minimumimpedance value Zmin is large, the range of a variation in impedancewhich matches with that variation size can be secured, and it is alsopossible to secure the variation range of the impedance of at least 200Ω, even if the minimum impedance value Zmin is small. This can ensure amore stable coagulation and hemostasis performance.

Fourth Embodiment

A fourth embodiment of this invention will now be discussed. Incoagulating a thin tissue, as coagulation progresses, short-circuitingis likely to occur at a clamped part. In this case, the current locallyflows to interfere with the progression of coagulation, but the currentis not large enough to activate the current limiter, thus disablingdetection of this short-circuited state. In this respect, the fourthembodiment is characterized in that the output is stopped upon detectionof short-circuiting of the electrodes from the rate of impedance changeor the impedance value. Specifically, the output is stopped when it isdetected that the rate of impedance change dZ becomes equal to orsmaller than−1000 Ω/sec as shown in FIG. 8, or that the impedance valueZ becomes equal to or smaller than 5 Ω as shown in FIG. 9.

The operation of the fourth embodiment will now be described referringto a flowchart in FIG. 10.

As the foot-operated switch 8 of the electrosurgical apparatus isswitched ON (step S29), initialization is executed (step S30). In thisinitialization, the output power P1=40 W input by an operator via thesetting input section 12 is set to the variable Pout associated with theoutput power. It is assumed that an initial rate of impedance change dz2has been set to−1000 Ω/sec and an initial impedance value Z2 has beenset to 5 Ω.

Next, it is determined if the foot-operated switch 8 has been switchedOFF (step S31). When the decision is “YES,” “0” is substituted into theoutput power Pout (step S32) after which this flow will be terminated.

When the decision in step S31 is “NO,” the impedance Z and the rate ofimpedance change dz are calculated (step S33). It is then determined ifthe calculated rate of impedance change dz is equal to or smaller thanthe initial rate of impedance change dZ2 (−1000 Ω/sec in this example)(step S34). When the decision is “YES,” “0” is substituted into theoutput power Pout (step S35), and the informing section 14 then outputsa sound (buzzer ON) from the speaker or turns on the LED (step S36) toinform the operator. This flow is then terminated.

When the decision in step S34 is “NO,” it is determined if the impedanceZ is equal to or smaller than the initial impedance value Z2 (5 Ω inthis example) (step S37). When the decision is “YES,” the flow proceedsto the aforementioned step S35. When the decision in step S34 is “NO,”the flow returns to step 31.

The above-described fourth embodiment is summarized as follows.

(1) The output is started and the impedance value Z and the rate ofimpedance change dZ are computed during outputting.

(2) When the impedance satisfies either one of the following conditions(a) and (b), which is considered as occurrence of short-circuiting, thebuzzer is activated or the LED is turned on and then the output isstopped.

(a) Rate of impedance change dZ≦−1000 Ω/sec.

(b) Impedance value Z≦5 Ω.

According to the above-described fourth embodiment, inadequatecoagulation can be detected reliably by detecting short-circuitingduring coagulation.

Fifth Embodiment

A fifth embodiment of this invention will be discussed below. The fifthembodiment is characterized by combining the automatic stop function atthe end of coagulation in any one of the first to third embodiments withthe short-circuiting detecting function of the fourth embodiment.

FIG. 11 is a flowchart illustrating the operation of the fifthembodiment. This flowchart corresponds to the flowchart in FIG. 4 towhich steps S44 to S47 that are carried out in the fourth embodiment areadded. A flowchart between A and B in FIG. 11 may be any one of theflowcharts in FIGS. 5 to 7. As the other steps in FIG. 11 are the sameas have been discussed above, their description will not be repeated.

According to this fifth embodiment, inadequate coagulation can bedetected by detecting the occurrence of short-circuiting during aprocess of detecting the end of coagulation and stopping the output.This can realize an automatic coagulation stop function with a higherprecision.

Sixth Embodiment

A sixth embodiment of this invention will now be described. Because theimpedance value significantly varies depending on the types of tissuesor the clamping state of forceps, a single load characteristic cannotprovide a stable coagulation performance. To deal with this shortcoming,the sixth embodiment is characterized in that the output characteristic(load characteristic) and output power are altered based on the initialimpedance value.

FIG. 12 is a flowchart illustrating the operation of the sixthembodiment. When the foot-operated switch 8 of the electrosurgicalapparatus is switched ON (step S49), initialization is implemented (stepS50). In this initialization, the output power for measuring theimpedance, P1=10 W, input by an operator via the setting input section12, is substituted into the variable Pout associated with the outputpower. It is assumed that another output power P2=40 W has been set.

Next, it is determined if 0.2 sec has elapsed (step S51). When 0.2 sechas passed, the impedance Z is calculated and the calculated impedance Zis substituted into the initial impedance value zini (step S52). It isthen determined if this initial impedance value Zini is equal to orgreater than 70 Ω (step S53). When the decision is “NO,” “100V” issubstituted into a voltage limiter value Vlim and “0.6 A” is substitutedinto a current limiter value Ilim. At the same time, the informingsection 14 starts outputting a sound (output sound 1) from the speaker(step S54).

When the decision in step S53 is “YES,” on the other hand, “60V” issubstituted into the voltage limiter value Vlim and “1.0 A” into thecurrent limiter value Ilim. At the same time, the informing section 14starts outputting a sound (output sound 2) from the speaker (step S55).Then, the previously set output power P2 (40 W in this example) issubstituted into the output power Pout (step S56), and it is thendetermined if the foot-operated switch 8 has been switched OFF (stepS57). When it is determined that the foot-operated switch 8 has beenswitched OFF, “0” is substituted into the output power Pout and theinforming section 14 stops outputting a sound from the speaker (stepS58).

Next, the meaning of the changing the output characteristic isexplained.

FIG. 26 shows an output characteristic when an output voltage and anoutput current are limited. A rising portion of an output characteristiccurve depends on the level of the current limitation (I lim) and a downportion of the output characteristic depends on the level of the voltagelimitation (V lim). When the current limitation is large, a slope of acharacteristic curve at the rising portion is steep. When the voltagelimitation is high, a slope of the characteristic curve at the downportion is steep.

In this sixth embodiment, when the impedance measured at step S52 ofFIG. 12 has proved to be high at step 53, the flow goes to step S55. Inthis case, the output characteristic of power supply unit shows a curveas shown by “a” in the FIG. 27. The power supply is mainly controlled inan “a-area” where the curve is decreasing. On the other hand, when themeasured impedance is low, the flow goes to step S54. In this case, theoutput characteristic of power supply unit shows a curve as shown by “b”in the FIG. 27. The power supply is mainly controlled in a “b-area”where the curve is increasing. In this way, the current and voltagelimitation are chosen so that the control is optimized.

The above-described sixth embodiment is summarized as follows.

(1) First, 10 W is output as the power for measuring the impedance andthe impedance value after 0.2 sec is set as the initial value.

(2) The voltage limiter value and the current limiter value are setbased on the initial impedance value Zini.

(a) When zini ≧70 Ω, the voltage limiter value Vlim=60V and the currentlimiter value Ilim=1.0 A.

(b) When Zini<70 Ω, the voltage limiter value Vlim=100V and the currentlimiter value Ilim=0.6 A.

(c) The output is made with the set power value. At this time, differentoutput sounds according to (a) and (b).

According to the above-described sixth embodiment, as the loadcharacteristic is changed in accordance with individual tissues, acoagulation performance which matches with each tissue can be provided.

Seventh Embodiment

A seventh embodiment of this invention will now be described withreference to FIG. 13. FIG. 13 is a flowchart for explaining theoperation of the seventh embodiment. When the foot-operated switch 8 ofthe electrosurgical apparatus is switched ON (step S59), initializationis implemented (step S60). In this initialization, the output power formeasuring the impedance, P1=10 W, input by an operator via the settinginput section 12, is substituted into the variable Pout associated withthe output power. It is assumed that other output powers P2=40 w andP3=20 w have been set.

Next, it is determined if 0.2 sec has elapsed (step S61). When 0.2 sechas passed, the impedance Z is calculated and the calculated impedance Zis substituted into the initial impedance value zini (step S62). It isthen determined if this initial impedance value Zini is equal to orgreater than 40 Ω (step S63). When the decision is “YES,” it isdetermined if the set power P2 is lower than the set power P3 (stepS64). When the decision is “NO,” the value of P3 is substituted into theoutput power Pout (step S65) and the flow then proceeds to step S67.When the decision in step S64 is “YES,” the value of P2 is substitutedinto the output power Pout (step S66) and the flow then proceeds to stepS67.

In step S67, the informing section 14 starts outputting a sound (outputsound 2 in this example) r from the speaker. It is then determined if 2sec has elapsed (step S68). When the decision is “NO,” it is thendetermined if the foot-operated switch 8 has been switched OFF (stepS69). When the decision here is “NO,” the flow returns to step S68, andwhen the decision is “YES,” the flow proceeds to step S72.

When the decision in step S63 is “NO” or the decision in step S68 is“YES,” on the other hand, the flow goes to step S70 to substitute theinitial power P2 (40 W in this example) into the output power Pout. Atthe same time, the informing section 14 starts outputting a sound(output sound 1 in this example) from the speaker. Then, it isdetermined if the foot-operated switch 8 is OFF (step S71). When it isdetermined that the foot-operated switch 8 is OFF, the flow proceeds tostep S72. In step S72, “0” is substituted into the output power Pout andthe sound output is stopped, then this flow is terminated.

The above-described seventh embodiment is summarized as follows.

(1) First, 10 W i s output as the power for measuring the impedance andthe impedance value after 0.2 sec is set as the initial value.

(2) When the initial impedance value Zini is less than 40 Ω, the outputis limited to 20 W or lower for 2 seconds after the measuring hascompleted. When the set power is equal to or greater than 20 W, 20 W isoutput, and when the set power is less than 20 W, the set power isoutput. After 2 seconds, the set power is output.

(3) when the initial impedance value zini is equal to or greater than 40Ω, the set power is output from the beginning.

(4) During output restriction in (2), the output sound 2 different fromthe normal output sound 1 is generated.

According to the above-described seventh embodiment , the first outputis limited low for a low-impedance tissue, so that outputs which matchwith the individual tissues can be made using the same loadcharacteristic. This can provide the coagulation performance suitablefor each tissue.

Although the output is stopped when a predetermined impedance conditionis met in this embodiment, this is not restrictive and the output may ofcourse be reduced.

The above-described first to seventh embodiments can provideelectrosurgical apparatuses which can more reliably stop the output atthe end of coagulation to avoid overburning.

Eighth Embodiment

An eighth embodiment is characterized in that the current condition forthe output control or stopping the output (automatic stop) is changed inaccordance with the coagulation level set by a user.

FIG. 14 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to the eighth embodiment. Thisstructure is quite the same as the one shown in FIG. 1 except that thevoltage sensor 19 in the structure in FIG. 1 is eliminated and insteadof the impedance calculator 20, an A/D converter 120 is connected to thecurrent sensor 18.

Although the bipolar instrument is illustrated as an instrument in FIG.14, the monopolar instrument 23 with the monopolar electrode 23 a may beused instead as shown in FIG. 2. In this case, the feedback electrode 25is connected to the terminal 21 b via the feedback line. The A/Dconverter 120 is connected between the output of the current sensor 18and the CPU 13. The CPU 13 is further connected to the foot-operatedswitch 8, the setting input section 12 and the informing section 14.

In the eighth embodiment, the high-frequency output is controlled bycontrolling the amplifier 15 by the CPU 13 and the output controller 16as the control section.

FIG. 15 is a diagram showing the structure of the setting input section12, which has a setting switch 12B for permitting the user to set acoagulation level and a coagulation level display section 12A fordisplaying the set coagulation level. Every time the setting switch 12Bis depressed, the coagulation level is displayed on the coagulationlevel display section 12A while changing in the order of 1→2→3→4→1 and acurrent value Istop=0.6 A, 0.5 A, 0.4 A or 0.2 A for stopping the outputis set in association with each coagulation level 1, 2, 3 or 4 set.

FIG. 16 shows the relationship between the characteristic of ahigh-frequency current (I) and the output of the power supply circuit 10and shows that the output of the amplifier 15 is stopped when thecurrent condition for stopping the output is met.

The operation of the eighth embodiment will be explained below referringto a flowchart in FIG. 17.

As the foot-operated switch 8 for initiating the steady power outputfrom the electrosurgical apparatus is switched ON (step S101),initialization is executed (step S102). In this initialization, theoutput power P1=40 W input by a user via the setting input section 12 issubstituted into the variable Pout associated with the output power, acoagulation level is set, and the current value Istop as the currentcondition for stopping the output is set. The set values input by theuser are stored in a memory section in the CPU 13 to be used in a nextsurgery.

Then, it is determined if the foot-operated switch 8 has been switchedOFF (step S103). When the foot-operated switch 8 has been switched OFF,“0” is substituted into the output power Pout (step S105) to stop thehigh-frequency output, and then this flow is terminated. When thefoot-operated switch 8 has not been switched OFF, the current value Idetected by the current sensor 18 is measured (step S104) and it is thendetermined if the measured current value I is lower than the set currentvalue Istop (step S106). When the decision is “NO,” the flow returns tostep S103. When the current value I measured after a predetermined timeis lower than the set current value Istop, the decision in step S106becomes “YES” so that the flow proceeds to step S107 where “0” issubstituted into the output power Pout to stop the high-frequencyoutput. At the same time, the informing section 14 outputs a sound(buzzer ON) from the speaker or turns on the LED (step S108) to informthe user after which this flow will be terminated.

According to the above-described eighth embodiment, the coagulationlevel in automatic stop mode can be changed in accordance with theuser's selection by altering the current condition for detecting the endof coagulation.

Ninth Embodiment

A ninth embodiment of this invention will be discussed below referringto the accompanying drawings. The ninth embodiment is characterized inthat the voltage condition for stopping the output is changed inaccordance with the coagulation level set by a user.

FIG. 18 is a diagram illustrating the internal structure of anelectrosurgical apparatus according to the ninth embodiment. Thisstructure is basically the same as that of the eighth embodiment exceptfor the voltage sensor 19 provided in place of the current sensor 18.

According to the ninth embodiment, the voltage condition can be set byusing the structure of the setting input section 12 as shown in FIG. 15.In this case, however, a voltage value Vstop=60V, 90V, 120V or 150V forstopping the output is set in association with each coagulation level 1,2, 3 or 4 set.

FIG. 19 shows the relationship between the characteristic of ahigh-frequency voltage (V) and the output of the power supply circuit 10and shows that the output of the amplifier 15 is stopped when thevoltage condition for stopping the output is met.

The operation of the ninth embodiment will now be discussed referring toa flowchart in FIG. 20.

As the foot-operated switch 8 for initiating the steady power outputfrom the electrosurgical apparatus is switched ON (step S111),initialization is executed (step S112). In this initialization, theoutput power P1=40 W input by a user via the setting input section 12 issubstituted into the variable Pout associated with the output power, acoagulation level is set, and the voltage value Vstop as the voltagecondition for stopping the output is set.

Then, it is determined if the foot-operated switch 8 has been switchedOFF (step S113). When the foot-operated switch 8 has been switched OFF,“0” is substituted into the output power Pout (step S115) to stop thehigh-frequency output, and then this flow is terminated. When thefoot-operated switch 8 has not been switched OFF, the voltage value Vdetected by the voltage sensor 19 is measured (step S114) and it is thendetermined if the measured voltage value V is higher than the setvoltage value Vstop (step S116). When the decision is “NO,” the flowreturns to step S113. When the voltage value V measured after apredetermined time is exceeds the set voltage value Vstop, the decisionin step S116 becomes “YES” so that the flow proceeds to step S117 where“0” is substituted into the output power Pout to stop the high-frequencyoutput. At the same time, the informing section 14 outputs a sound(buzzer ON) from the speaker or turns on the LED (step S118) to informthe user after which this flow will be terminated.

According to the above-described ninth embodiment, the coagulation levelin automatic stop mode can be changed in accordance with the user'sselection by altering the voltage condition for detecting the end ofcoagulation.

Tenth Embodiment

A tenth embodiment of this invention will be discussed below referringto the accompanying drawings. The tenth embodiment is characterized inthat the impedance condition for stopping the output is changed inaccordance with the coagulation level set by a user.

The internal structure of an electrosurgical apparatus according to thetenth embodiment is the same as the above-described structure shown inFIG. 1. This structure is the combination of the above-describedstructures shown in FIGS. 14 and 18 except for the impedance calculator20 provided in place of the A/D converter 120.

This tenth embodiment can likewise set the impedance condition by usingthe structure of the setting input section 12 as shown in FIG. 15. Inthis case, however, three variables P_dz (rate of impedance change(Ω/sec)), P_mZ (multiplier constant) and P_Z (impedance value (Ω)) areused as the impedance conditions to be set for stopping the output, andare determined as follows in association with each coagulation level 1,2, 3 or 4 set.

coagulation level 1: P_dZ=300, P_mZ=3, P_Z=300

coagulation level 2: P_dZ=400, P_mZ=3, P_Z=400

coagulation level 3: P_dz=500, P_mZ=4, P_Z=500

coagulation level 4: P_dZ=600, P_mZ=4, P_Z=600

FIG. 3 shows the relationship between the characteristic of theimpedance (Z) and the output of the power supply circuit 10 and showsthat the output of the amplifier 15 is stopped when the impedancecondition is met.

The operation of the tenth embodiment will now be discussed referring toa flowchart in FIG. 21.

As the foot-operated switch 8 for starting the steady power output fromthe electrosurgical apparatus is switched ON (step S121), initializationis carried out (step S122). In this initialization, the output powerP1=40 w input by a user via the setting input section 12 is set to avariable Pout associated with the output power and 10 KΩ is set to avariable Zmin associated with the minimum impedance value. Further,P_dZ, P_mZ and P_Z set by the user in association with the coagulationlevel are set. In addition, the decision variable Cn1=0 and decisionvariable Cn2=0 are set.

Then, it is determined if the foot-operated switch 8 has been switchedOFF (step S123). When the foot-operated switch 8 has been switched OFF,“0” is set to the output power Pout (step S125) to stop thehigh-frequency output after which this flow will be terminated. When thefoot-operated switch 8 has not been switched OFF, the impedance Z andthe rate of impedance change dZ are calculated (step S124). Next, it isdetermined if the calculated impedance z is smaller than the minimumimpedance value Zmin (step S126). When the decision is “YES,” thecalculated impedance Z is substituted into the minimum impedance valueZmin (step S127) and then the flow returns to step S123.

When the decision in step S126 is “NO,” on the other hand, the flowproceeds to step S128 in FIG. 22 to determine if the calculated rate ofimpedance change dZ is equal to or greater than P_dZ. When the decisionis “YES,” “1” is substituted into the decision variable Cn1 (step S129)and the flow then goes to step S130. When the decision in step S128 is“NO,” the flow immediately proceeds to step S130.

In step S130, it is determined if the impedance Z is equal to or greaterthan the minimum impedance value Zmin multiplied by the multiplierconstant P_m. When the decision is “YES,” “1” is substituted into thedecision variable Cn2 (step S131) and the flow then proceeds to stepS132. When the decision in step S130 is “NO,” the flow immediatelyproceeds to step S132.

In step S132, it is determined if Cn1×Cn2 is equal to “1.” When thedecision is “YES,” “0” is substituted into the output power Pout (stepS133) to stop the high-frequency output, and the informing section 14outputs a sound (buzzer ON) from the speaker or turns on the LED (stepS134) to inform the user. This flow is then terminated.

When the decision in step S132 is “NO,” it is determined if theimpedance Z is equal to or greater than the sum of the minimum impedancevalue Zmin and the initial impedance value P_Z (step S135). When thedecision is “YES,” the processes starting at the aforementioned stepS133 are executed. When the decision in step S135 is “NO,” the flowreturns to step S123 in FIG. 21.

As apparent from the above, the tenth embodiment stops thehigh-frequency output when the impedance satisfies either one of thefollowing conditions (a) and (b).

(a) The rate of impedance change dZ has become equal to or greater thanP_dZ at least once and the impedance value Z has become equal to orgreater than the product of the minimum impedance value Zmin and P_m.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and P_Z.

According to the above-described tenth embodiment, the coagulation levelin automatic stop mode can be changed in accordance with the user'sselection by altering the impedance condition for detecting the end ofcoagulation.

Eleventh Embodiment

An eleventh embodiment of this invention will be discussed belowreferring to the accompanying drawings. The eleventh embodiment ischaracterized in that the delay time for stopping the output is changedin accordance with the coagulation level set by a user.

The internal structure of an electrosurgical apparatus according to theeleventh embodiment is the same as that of the tenth embodiment. Theeleventh embodiment can likewise use the structure of the setting inputsection 12 as shown in FIG. 15 to set the delay time for stopping theoutput. In this case, however, the delay time for stopping the output isset to T=0 sec, 1 sec, 2 sec or 3 sec in association with eachcoagulation level 1, 2, 3 or 4 set. P_dZ (rate of impedance change),P_mZ (multiplier constant) and P_Z (impedance value) as the impedanceconditions are fixed to P_dZ=300 (Ω/sec), P_mZ=3 and P_Z=500 (Ω).

The operation of the eleventh embodiment of this invention will bediscussed below. While the flowchart in FIG. 21 is commonly used todescribe the operation of the eleventh embodiment, the delay time T isset in the initialization in step S122. The difference lies in that aflowchart shown in FIG. 23 is used in the eleventh embodiment as aflowchart showing steps between A and B in FIG. 21. As the flowchart inFIG. 21 has already been discussed, only the flowchart in FIG. 23 willbe discussed below. First, it is determined in step S138 if thecalculated rate of impedance change dZ is equal to or greater than P_dZ(300 Ω/sec in this example). When the decision is “YES,” “1” issubstituted into the decision variable Cn1 (step S139) and the flow thenmoves to step S140. When the decision in step S138 is “NO,” the flowimmediately proceeds to step S140.

In step S140, it is determined if the impedance Z is equal to or greaterthan the minimum impedance value Zmin multiplied by the multiplierconstant P_m (3 in this example). When the decision is “YES,” “1” issubstituted into the decision variable Cn2 (step S141) and the flow thenproceeds to step S142. When the decision in step S140 is “NO,” the flowimmediately proceeds to step S142.

In step S142, it is determined if the product of Cn1 and Cn2 is equal to“1.” When the decision is “YES,” the flow proceeds to step S144 to waitfor the delay time T to elapse. When the delay time T elapses, thedecision in step S144 becomes “YES” and the flow then goes to step S145.In step S145, “0” is substituted into the output power Pout to stop thehigh-frequency output, and the informing section 14 outputs a sound(buzzer ON) from the speaker or turns on the LED (step S146) to informthe user. This flow is then terminated.

When the decision in step S142 is “NO,” the flow proceeds to step S143to determine if the impedance Z is equal to or greater than the sum ofthe minimum impedance value Zmin and the initial impedance value P_Z(500 Ω in this example). When the decision is “YES,” the processesstarting at the aforementioned step S144 are executed. When the decisionin step S143 is “NO,” the flow returns to step S123 in FIG. 21.

As apparent from the above, the eleventh embodiment stops thehigh-frequency output when the delay time T elapses after the impedancesatisfies either one of the following conditions (a) and (b).

(a) The rate of impedance change dZ has become equal to or greaterthan+300 Ω/sec at least once and the impedance value Z has become equalto or greater than the minimum impedance value Zmin multiplied by 3.

(b) The impedance value Z has become equal to or greater than the sum ofthe minimum impedance value Zmin and 500 Ω.

The above-described eleventh embodiment has such an effect that there isno variation in detection due to the same threshold value (current,voltage, impedance or the like) used in addition to changing thecoagulation level in automatic stop mode in accordance with the user'sselection of the delay time.

Twelfth Embodiment

A twelfth embodiment of this invention will be discussed below. Thetwelfth embodiment is the combination of the eighth to eleventhembodiments, and FIG. 24 illustrates the internal structure of anelectrosurgical apparatus according to the twelfth embodiment. Thesetting input section 12 in this case takes a structure as shown in FIG.25, so that a user can designate an appropriate output stop condition bydepressing a one of a current select button 12C, a voltage select button12D, an impedance select button 12E and a delay-time select button 12F.The user can then set the coagulation level by depressing the settingswitch 12B. After the above setting is made, a sequence of processeswill be carried out according to each setting and each of the combinedembodiments.

The above-described twelfth embodiment can set the desired output stopcondition.

The above-described eighth to twelfth embodiments can provideelectrosurgical apparatuses which are able to change the coagulationlevel according to a user's selection by changing the condition fordetecting the end of coagulation.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. The electrosurgical apparatus for supplyinghigh-frequency power from a high-frequency power supply unit to aninstrument placed in association with an organic tissue to dissect orcoagulate said organic tissue comprising: an impedance calculatingsection for calculating an impedance value of said organic tissue beforethe instrument starts to coagulate or dissect said organic tissue; and aload characteristic alternating means which selects a loadcharacteristic of an output in accordance with an initial impedancevalue of the organic tissue calculated by said impedance calculatingsection, wherein said load characteristic altering section selects afirst load characteristic in which a load characteristic of an outputhas a peak at a predetermined impedance in a case where the initialimpedance value of the organic tissue calculated by the impedancecalculating section is above a designated threshold value, and selects asecond load characteristic in which a load characteristic of an outputhas a peak at an impedance higher than that of the first loadcharacteristic in a case where the initial impedance value of theorganic tissue is under the predetermined threshold value.
 2. Anelectrosurgical apparatus for supplying high-frequency power from ahigh-frequency power supply unit to an instrument placed in associationwith an organic tissue to dissect or coagulate said organic tissue,comprising: an impedance calculating section for calculating an initialimpedance value of said organic tissue before the instrument is startedto coagulate or dissect said organic tissue; and a load characteristicaltering section for changing at least one of a current limiter valueand a voltage limiter value in accordance with said initial impedancevalue of said organic tissue calculated by the impedance calculatingsection.
 3. An electrosurgical apparatus for supplying high-frequencypower from a high-frequency power supply unit to an instrument placed inassociation with an organic tissue to coagulate or dissect said organictissue, comprising: a detection section for detecting a coagulationstate of said organic tissue in a coagulation operation; a delay-timesetting section for randomly selecting and setting prior to acoagulation operation of the organic tissue, a delay time until ahigh-frequency output is stopped after the detection section hasdetected the coagulation state; and a section for calculating athreshold value for controlling said high-frequency output by detectinga high-frequency current and a high-frequency voltage from saidhigh-frequency power supply unit and said high-frequency output iscontrolled when a variable delay elapses after the threshold value hasbeen reached.
 4. The electrosurgical apparatus according to claim 3,further comprising an informing section for informing a user at a timeof controlling said high-frequency output of such control by at leastone of an acoustic method and a visual method.